1. Field of the Invention
This invention relates to an organic light emitting display (OLED), and more particularly, to an OLED with a high contrast ratio on the display screen and a longer life time.
2. Description of the Prior Art
In various types of flat panel displays, since an OLED, being developed later than a liquid crystal display (LCD), has many beneficial characteristics, such as having a spontaneous light source, a wide viewing angle, high response velocity, power saving, strong contrast, high brightness, small thickness, full-color, simpler structure, and a wide operating temperature, the OLED has been used extensively in small and medium scale portable display fields. After continuous research and development by manufacturers and scholars, the break through of some unresolved problems, such as low yield rate, unsatisfied mask application, unstable cap seal, has provided eminent progress.
Since the conductors, electrodes, or other patterns made of metal in the OLED may reflect lights, its display images often has low quality caused by its unfavorable contrast ratio when the OLED is operated in an environment with strong ambient light. To improve the contrast ratio of the display images, according to the prior art, a polarizer is placed on the surface of the substrate of the OLED to reduce the reflection of the ambient light. However, although the polarizer may reduce the reflection of the ambient light effectively, at the mean time the penetration rate of the light produced by the OLED itself may be reduced to 42%, which causes the insufficient luminous efficiency. In addition, to compensate the deficient brightness of the display images caused by the insufficient luminous efficiency, high voltage has to be provided to the organic emitting elements to increase their luminosity. As a result, its power consumption is increased and the life time of the internal elements of the OLED is shortened. Therefore, the prior method of setting up a polarizer on the surface of the substrate still has its shortcoming which is that it cannot meet both the contrast ratio and luminosity requirement and the low power consumption requirement of the display.